1. Field of the Invention
This invention relates generally to an inflatable mattress, particularly for use in the treatment of patients in hospitals, nursing homes and home care.
2. Description of the Prior Art
Treatment of bedridden patients has long been adversely compounded due to improper support or pressure from the mattress on which the patient rests. Unfortunately, conventional mattresses obstruct both the flow of air to the skin and the dissipation of heat away from the affected area. Additionally, the support provided by such mattresses typically causes much pain to the extremely sensitive and vulnerable areas of the patient's skin.
Another widely known complication resulting from improper mattress support is the development of decubitus ulcers or bedsores. Decubitus ulcers are localized areas of cellular necrosis, or localized death of the skin, which tend to occur between skeletal boney prominances and the compressive mattresses surface upon which the patient rests, such as a mattress. This compressive force, when in excess of the capillary hydrostatic pressure for more than one or two hours, produces tissue ischemia which cannot be compensated by the mechanism of reactive hyperemia. As a result, irreversible pathological destruction occurs in the tissues, leading to death of the latter.
Other physical factors which contribute to production of decubitus ulcers, in addition to the compressive force as hereinabove mentioned, are (1) a shearing force which stretches soft tissue disposed between the bone and a segment of immovabale skin, such that the blood vessels thereby stretched are blocked and in time cause extensive tissue destruction, (2) heat, commonly caused by a fever which increases the metabolic rate of the body and increases the oxygen demand, the supply of which to the skin may already be compromised by the compressive forces, (3) moisture, in the form of perspiration or incontinence, which reduces the resistance of the skin to other physical stresses, (4) friction or abrasion injury which usually results in a loss of epidermis and also may break the integrity of the skin surface such that infection, edema and increased moisture may result, and (5) poor hygiene, wherein bacteria localized in ischemic tissues multiply rapidly and prolong the healing process of the ulcer. Obviously, all such factors are highly dependent upon the characteristics of the mattress or support on which the patient rests.
A variety of mattresses have been proposed in the past in an attempt to provide proper support for a burn victim or patient with decubitus ulcers. Water or gel filled beds, for example, somewhat equalize pressure distribution over the entire body but have no provision for circulating air, removing moisture or dissipating heat from the contacted skin area. Also, the manipulation of the patient on the water bed is difficult, and such beds are extremely heavy and precluded from use in many older buildings.
Several devices have previously been proposed for suspending recumbent patients on a cushion of air such that all contact with a mattress is eliminated. Unfortunately, such devices have not proved to be practical because the high velocity of the rising air column required to support the person tends to damage the healing areas by continual erosion. Additionally, such devices require large amounts of air, expensive pressure regulators and constant adjustment.
Air filled mattresses have also been proposed in the past for use with bedridden patients. U.S. Pat. No. 3,778,851 discloses a mattress having a plurality of somewhat resilient, internal synthetic resin spines, each surrounded by an elongated inflatable rib section which has a plurality of upper airflow apertures. The juxtaposed rib sections are in turn supported by an underlying block of formed plastic material, and the entire assembly is encased in a mattress cover. A continuously flowing airstream inflates the ribs and also escapes through the apertures to cool and ventilate the patient. However, the mattress of the '851 patent does not provide true air flotation support. Rather, the body weight of the patient compresses the rib sections and forces the latter into engagement with the underlying plastic support. As a consequence, the patient is in reality supported by the elongated spines and the lower solid support. It is therefore believed that this mattress construction suffers from many of the aforementioned problems, i.e., it does not provide patient support with the complete absence of substantial weight-supporting internal elements. Moreover, it appears that this mattress construction may inhibit the flow of cool, healing air to the areas of the skin adjacent the mattres and the dissipation of detrimental moisture and heat in all areas of the body.
Accordingly, there is a serious need in the art for a mattress which evenly distributes the weight of the body without the necessity of internal spines or other patient-contacting solid supports. Additionally, the ideal mattress would permit airflow to all areas of the skin to absorb moisture and prevent heat accumulation, yet have a smooth, soft surface and an inexpensive, maintenance-free construction.